Medium-voltage switchgear system having single phase breaker control

ABSTRACT

A medium-voltage switchgear system includes a three-phase circuit breaker having first, second and third single-phase vacuum interrupters connected between respective first, second and third single-phase inputs and first, second and third single-phase outputs. Magnetic actuators are connected to first, second and third single-phase vacuum interrupters, which are configured to receive an interrupt signal and in response, actuate the respective vacuum interrupter connected thereto into an open circuit condition. A controller circuit is connected to each of the first, second and third magnetic actuators and generates an interrupt signal in response to a detected single-phase overcurrent or fault on a single-phase circuit and interrupt that single-phase circuit on which the single-phase overcurrent or fault occurred and maintain power on the remaining two single-phase circuits over which a single-phase overcurrent or fault was not detected.

PRIORITY APPLICATION(S)

This is a continuation application based upon U.S. Pat. ApplicationSerial No. 17/422,825 filed Jan. 26, 2022, which is a 35 U.S.C. §371national phase application, which is based upon internationalApplication No. PCT/CN2021/089905 filed Apr. 26, 2021, which is basedupon U.S. Provisional Application Serial No. 63/153,419 filed Feb. 25,2021, the disclosures which are hereby incorporated by reference intheir entirety.

FIELD OF THE INVENTION

The present invention relates to electrical systems, and moreparticularly, to electrical switchgear systems.

BACKGROUND OF THE INVENTION

Metal-clad or metal-enclosed medium voltage switchgear systems operateas three-phase systems that connect to the three-phase powerdistribution grid and provide various control functions and provideprotection against short circuit events and similar overcurrent or otherfault conditions. These switchgear systems include transformers toreduce the primary circuit voltage, which can be greater than 1,000volts, to a much lower voltage that may energize control circuits ormonitor or meter the primary voltage. These switchgear systems andassociated load circuits may be protected from damage by a fuse when thetransformers fail. The transformers and fuses may be mounted together asan assembly on a truck that is movable as a platform within theswitchgear frame and associated interior compartment.

The truck may include wheels that ride on rails on either side of theswitchgear frame. The transformer and any associated fuses occasionallyneed to be checked or serviced, which requires access to thesecomponents. The transformer and fuses are mounted on the truck, whichallows for the connection and disconnection of electrical circuits fromthe transformer and fuses by racking out the truck. After disconnection,existing techniques to access the transformers and fuses for maintenanceand service require the transformer and fuse as an assembly to becompletely removed from the switchgear system using extension rails thatextend outward from the switchgear frame or a lift-truck. The lift-truckmay be cumbersome and the extension rails may deflect. Thus,improvements are desirable.

Switchgear systems also use circuit breakers, which open and closeindividual circuits and are mounted on a truck. These circuit breakersmay be connected and disconnected not only from primary circuits, butalso may be connected and disconnected from the secondary control powercircuit. The manner in which the circuit breaker moves between thesepositions, such as a connected, a test, and a disconnected position, isoften important to its ability to operate as a circuit breaker and bemaintained as part of the service of the switchgear system.

Short circuit events and similar overcurrent or other fault conditionsmay generate very large currents, which places physical stresses on thecircuit breaker and the racking system that includes the truck thatracks in and racks out the circuit breaker from the electricallyconnected, test, and disconnected positions. Further improvements wouldbe advantageous to support movement of the circuit breakers on the truckand created more stable operation, especially when there are shortcircuit events or similar overcurrent or other fault conditions.

Many switchgear systems include shutters that fail closed and coverprimary circuit contacts, but sometimes cause sparks and burning. Inrare cases when they fail in a closed position, there may be anexplosion. Failing open has not always been an option, even though thecircuit breakers are racked in 97–99% of the time. Also, when requiringmaintenance on a circuit breaker, the shutters should be closed toprotect an operator or maintenance worker from contacting the primarycircuit contacts. Further improvements in shutter design for switchgearsystems would be advantageous.

Metal clad switchgear systems usually include at least one or moreinterior compartments that contain transformers, circuit breakers, andother electrical components, and often include an adjacent main buscompartment, including a cable compartment. High heat is often generatedin these interior compartments, especially during a fault or shortcircuit event that creates arcing conditions. The switchgear systemincludes these interior compartments that are sometimes difficult tovent.

In some cases, the buses are difficult to cool because the buses aresometimes aligned along a common X-axis in a vertically stackedarrangement, causing hot air from lower buses to heat up the upperbuses. Some switchgear systems include arc-resistant interiorcompartments, but it is important to vent these compartments to minimizetemperature rises. Fans and other powered cooling devices may be used,but convective cooling in some cases is preferred. Further improvementsin ventilation systems are desired.

The switchgear systems that include a truck carrying a circuit breakermay include contact arms that are used to connect the circuit breaker tocontacts of the circuit breaker truck and engage stationary contactsconnected to a primary circuit, which may include one or more busconnections. Some contact arms include annular rings disposed in spacedrelation for convective heat rejection. These annular rings depending ontheir configuration may cause high electrostatic field stresses andshorter flash over path links to grounded objects in the switchgearsystem. These high amperage circuit breakers and switchgear contactfingers are a source of heat and excess temperature rises may causefailures. Improvements in configuration for contact arm assemblies thatwould impart better heat conduction would be advantageous.

SUMMARY OF THE INVENTION

This summary is provided to introduce a selection of concepts that arefurther described below in the Detailed Description. This summary is notintended to identify key or essential features of the claimed subjectmatter, nor is it intended to be used as an aid in limiting the scope ofthe claimed subject matter.

In general, a medium-voltage switchgear system may comprise a switchgearframe having an interior compartment and first, second and thirdsingle-phase inputs and first, second and third single-phase outputsconnected to respective first, second and third single-phase circuits ofa three-phase power distribution grid. A three-phase circuit breaker maycomprise first, second and third single-phase vacuum interruptersconfigured to be connected between respective first, second and thirdsingle-phase inputs and first, second and third single-phase outputs. Afirst magnetic actuator may be connected to the first single-phasevacuum interrupter, a second magnetic actuator may be connected to thesecond single-phase vacuum interrupter, and a third magnetic actuatormay be connected to the third single-phase vacuum interrupter. Eachmagnetic actuator may be configured to receive an interrupt signal andin response, actuate the respective vacuum interrupter connected theretointo an open circuit condition. A controller circuit may be connected toeach of the first, second and third magnetic actuators, and configuredto generate the interrupt signal to a respective magnetic actuator inresponse to a detected single-phase overcurrent or fault on asingle-phase circuit and interrupt that single-phase circuit on whichthe single-phase overcurrent or fault occurred and maintain power on theremaining two single-phase circuits over which a single-phaseovercurrent or fault was not detected.

The controller circuit may comprise a first controller mounted withinthe interior compartment and connected to the first magnetic actuator, asecond controller mounted within the interior compartment and connectedto said second magnetic actuator and a third controller mounted withinthe interior compartment and connected to said third magnetic actuator.In another example, the controller circuit may comprise a controllermounted within the interior compartment and connected to each of saidfirst, second and third magnetic actuators. First, second and thirdloads may be connected to respective first, second and thirdsingle-phase outputs. The first, second and third loads each maycomprise a plurality of floors in an apartment building having anelectrical demand operating with single-phase power.

The first, second and third loads may comprise a business usingthree-phase power and a group of homes using single-phase power. Asensing circuit may be connected to the first, second and thirdsingle-phase outputs and configured to detect a single-phase overcurrentor fault on said first, second and third single-phase circuits. Thesensing circuit may comprise at least one current or potentialtransformer.

In yet another example, a medium-voltage switchgear system may comprisea switchgear frame having an interior compartment and first, second andthird single-phase inputs and first, second and third single-phaseoutputs connected to respective first, second and third single-phasecircuits of a three-phase power distribution grid. A truck andthree-phase circuit breaker may be carried thereon and supported formovement on the switchgear frame. The three-phase circuit breaker maycomprise first, second and third single-phase vacuum interruptersconfigured to be connected between respective first, second and thirdsingle-phase inputs and first, second and third single-phase outputs. Adrive mechanism may be mounted on the switchgear frame and connected tothe truck and configured to rack the truck and first, second and thirdsingle-phase vacuum interrupters into electrical connection with therespective first, second and third single-phase inputs and first, secondand third single-phase outputs. A first magnetic actuator may beconnected to the first single-phase vacuum interrupter, a secondmagnetic actuator may be connected to the second single-phase vacuuminterrupter, and a third magnetic actuator may be connected to the thirdsingle-phase vacuum interrupter. Each magnetic actuator may beconfigured to receive an interrupt signal and in response, actuate therespective vacuum interrupter connected thereto into an open circuitcondition. A controller circuit may be connected to each of the first,second and third magnetic actuators, and configured to generate theinterrupt signal to a respective magnetic actuator in response to adetected single-phase overcurrent or fault on a single-phase circuit andinterrupt that single-phase circuit on which the single-phaseovercurrent or fault occurred and maintain power on the remaining twosingle-phase circuits over which a single-phase overcurrent or fault wasnot detected.

A method aspect of operating a medium-voltage switchgear system maycomprise connecting first, second and third single-phase inputs andfirst, second and third single-phase outputs contained within aninterior compartment of a switchgear frame to respective first, secondand third single phase circuits of a three-phase power distributiongrid. The method further includes connecting first, second and thirdsingle-phase vacuum interrupters of a three-phase circuit breakerbetween the respective first, second and third single-phase inputs andfirst, second and third single-phase outputs, and receiving an interruptsignal within one of a first magnetic actuator connected to the firstsingle-phase vacuum interrupter, a second magnetic actuator connected tothe second single-phase vacuum interrupter, and a third magneticactuator connected to the third single-phase vacuum interrupter, and inresponse, actuating a respective vacuum interrupter connected theretointo an open circuit condition. The method may include generating theinterrupt signal via a controller circuit connected to each of saidfirst, second and third magnetic actuators, and configured to generatethe interrupt signal to a respective magnetic actuator in response to adetected single-phase overcurrent or fault on a single-phase circuit ofthe three-phase power distribution grid and interrupt that single-phasecircuit on which the single-phase overcurrent or fault occurred andmaintain power on the remaining two single-phase circuits over which asingle-phase overcurrent or fault was not detected.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features and advantages of the present invention willbecome apparent from the Detailed Description of the invention whichfollows, when considered in light of the accompanying drawings in which:

FIG. 1 is an isometric view of an electrical switchgear system, inaccordance with a non-limiting example, showing front and rearswitchgear sections having first and second sets of front and rear upperand lower switchgear housings joined together.

FIG. 2A is a front isometric view of a portion of the switchgear systemof FIG. 1 and showing a front, upper switchgear housing having upper andlower compartments and showing trucks racked in the electricallyconnected position.

FIG. 2B is another front isometric view of the switchgear system similarto that shown in FIG. 2A and showing the trucks racked out to thedisconnected position.

FIG. 3 is another front isometric view of the switchgear system similarto that of FIGS. 2A and 2B and showing the trucks racked out to therotated position.

FIGS. 4A through 4C are partial rear isometric views of the trucks inthe upper compartment of FIGS. 2A, 2B and 3 , and showing the respectiveconnected, disconnected, and rotated positions.

FIG. 5 is an enlarged rear isometric view of the truck of FIG. 4C in therotated position.

FIGS. 6A through 6C are side elevation views of the top compartment ofthe switchgear system of FIGS. 2A, 2B and 3 showing the truck in theconnected (FIG. 6A), disconnected (FIG. 6B), and rotated (FIG. 6C)positions.

FIG. 7 is a plan view of the drive mechanism shown in FIG. 2A connectedto the truck.

FIG. 8 is a partial side sectional view of the drive mechanism of FIG. 7.

FIG. 9A is a side elevation view of a section of a circuit breaker drivemechanism mounted in the lower, front switchgear housing of FIG. 1 andconnected to another linearly movable circuit breaker truck that carriesa circuit breaker as illustrated and showing it racked into a firstelectrically connected position.

FIG. 9B is another side elevation view of the circuit breaker drivemechanism and truck of FIG. 9A and carrying a circuit breaker andshowing a partial cut-away section view of the drive chain.

FIG. 10 is a top plan view in partial cut-away section of the circuitbreaker drive mechanism and showing a portion of the drive chain.

FIG. 11 is a side sectional view of the circuit breaker drive mechanismof FIG. 9A showing the drive chain, shuttle and first and secondsprockets interconnecting the drive chain.

FIG. 12 is another top plan view in full cut-away section showing thecircuit breaker drive mechanism and the drive chain and worm drive.

FIG. 13 is an isometric view of the circuit breaker drive mechanismshowing a partial cut-away of the drive chain and shuttle.

FIG. 14 is an isometric view showing a portion of the interiorcompartment of the front, lower switchgear housing section showing theswitchgear frame, circuit breaker drive mechanism and its drive chainand shuttle, and rails on the switchgear frame for supporting therollers of the circuit breaker truck.

FIG. 15 is a side elevation view of the truck carrying a circuit breakerin electrical connection with the primary circuit contacts, and showingthe open shutter.

FIG. 16 is another side elevation view of the circuit breaker drivemechanism and truck carrying the circuit breaker and the shutter closedover the primary circuit contacts when the circuit breaker drivemechanism racks out the circuit breaker.

FIG. 17 is an isometric view of a portion of the circuit breaker drivemechanism and interconnected shutter mechanism.

FIG. 18 is a partial schematic isometric and sectional view of a contactarm assembly, such as may be used for the switchgear circuit breaker asshown in FIG. 16 .

FIG. 19 is a schematic isometric view of the electrical switchgearsystem of FIG. 1 showing front and rear switchgear sections and thecentral ventilation duct that may be incorporated within the electricalswitchgear system.

FIG. 20 is another schematic, isometric view of the switchgear systemshown in FIG. 19 and showing by arrows the convective flow of air andgases out of the interior compartments and through the centralventilation duct.

FIG. 21 is a side elevation view of the switchgear system of FIG. 19 .

FIG. 22 is a bottom plan view of the switchgear system of FIG. 19 .

FIG. 23 is a top plan view of the switchgear system of FIG. 19 showingthe central ventilation duct.

FIG. 24 is a sectional view taken along line 24-24 of FIG. 23 showingthe central ventilation duct.

FIG. 25 is an enlarged view of the circled section of FIG. 24 showingthe air and gas venting into the central ventilation duct.

FIG. 26 is a partial sectional view of the switchgear system taken alongline 26-26 of FIG. 1 showing in greater detail the central ventilationduct and vent covers to direct air and gas by convection out of theventilation duct.

FIG. 27 is a block diagram of a three-phase power distribution gridincorporating a medium-voltage switchgear system having single-phasebreaker control.

DETAILED DESCRIPTION

Different embodiments will now be described more fully hereinafter withreference to the accompanying drawings, in which preferred embodimentsare shown. Many different forms can be set forth and describedembodiments should not be construed as limited to the embodiments setforth herein. Rather, these embodiments are provided so that thisdisclosure will be thorough and complete, and will fully convey thescope to those skilled in the art.

Referring now to FIG. 1 , there is illustrated generally at 100 anelectrical switchgear system in accordance with a non-limiting examplethat includes a front switchgear section 102 having first and secondsets of front upper and lower switchgear housings 104, 106, 108, 110 andhaving joined sidewalls. Referring also to FIG. 1 , and the moreschematic representation of the switchgear system 100 shown in FIGS.19-24 , a rear switchgear section 114 includes first and second sets ofrear upper and lower switchgear housings 116, 118, 120, 122 havingjoined sidewalls and connected to the rear of the respective front upperand lower switchgear housings 104, 106, 108, 110.

As will be explained in greater detail below, joined sidewalls of firstand second sets of front upper and lower switchgear housings 104, 106,108, 110, 116, 118, 120, 122 include a stepped offset section 130 asshown best in FIGS. 2A, 2B, 3 and 23 to form a ventilation duct 134extending the height of the switchgear system 100. Each switchgearhousing 104, 106, 108, 110, 116, 118, 120, 122 includes a switchgearframe 124 that defines an interior compartment 128 as best shown inFIGS. 2A, 2B and 3 .

It is possible that front and rear switchgear sections 102, 114 mayinclude “n” sets of both front and rear upper and lower switchgearhousings and form a series of switchgear housing sections forming theelectrical switchgear system 100. In an example as shown in FIGS. 2A, 2Band 3 , the left front upper switchgear housing 104 may include withinthe interior compartment 128 upper and lower compartments 136, 138 whereeach of the upper and lower compartments may include the front opening140 defined at the front of the switchgear housing 104 and a truck 144and drive mechanism 146 as shown in greater detail relative to FIGS. 2A,2B, 3, 4A-4C, 5, 6A-6C, 7, and 8 . The front left lower switchgearhousing 106 includes a circuit breaker truck 150 and circuit breakerdrive mechanism 152 such as explained below in the more detaileddescription of FIGS. 9A, 9B, and 10-17 .

The front switchgear section 102 upper and lower switchgear housings104, 106, 108, 110 and rear switchgear section 114 upper and lowerswitchgear housings 116, 118, 120, 122 each may include one or moreinterior compartments 128 and various electrical switchgear components.On the outside of the electrical switchgear system 100, and moreparticularly, on the outer side of the rear housings 120,122 as shown inFIG. 1 , there are shown components that make up part of a main busextension assembly and phased shorting bus 156 that may extend from amain bus compartment.

The rear switchgear section 114 may include in the various interiorcompartments of the switchgear housings 116, 118, 120, 122 a main busassembly, a ground bus assembly interconnect, a potential transformer(PT) and control power transformer (CPT) jump bus assembly, a line busassembly, a cable compartment, various bus bars and other associatedelectric components. The front section upper and lower switchgearhousings 104, 106, 108, 110 include doors 104 a, 106 a, 108 a, 110 a foreach switchgear housing to permit access into each interior compartment.

Referring now to FIGS. 2A, 2B and 3 , there is illustrated the frontswitchgear housing 104 of the electrical switchgear system 100 of FIG. 1and showing a switchgear frame 124 that includes a metal-clad housingand defines the upper and lower interior compartments 136, 138 andincludes a front opening 140. Each of the upper and lower compartments136, 138 includes a translatable and rotatable truck 144 that is movableon the switchgear frame 124 via a drive mechanism 146. The truck 144 inthis example may also be referred to as a draw-out auxiliary tray, buthereinafter will be referred to as the truck.

As shown in FIGS. 2A, 2B and 3 , the switchgear frame 124 defines withinthe interior compartment 128 the upper and lower interior compartments136, 138, and each part of the interior compartment 128 having its frontopening 140, formed similar to a box housing structure. In the exampleof the electrical switchgear system 100 of FIG. 1 , individualswitchgear housings may be stacked or placed side-by-side with otherswitchgear housings as shown in the example of the electrical switchgearsystem of FIG. 1 .

In this example of the switchgear housing 104 of FIGS. 2A, 2B and 3 ,the switchgear housing as part of the electrical switchgear system 100has its switchgear frame 124 and interior compartment 128 defining theupper and lower interior compartments 136, 138. Each of the upper andlower interior compartments 136, 138 may include at least one electricalswitchgear component, which could be any variety of electricalcomponents used in electrical switchgear systems, such as a connector toother devices, primary and/or secondary circuits, and associatedcontacts, including various electrical buses and control circuits. Theelectrical switchgear system 100 as explained above may include separatebus or cable compartments as part of the different switchgear housingsand may be integrated with other switchgear housings and includeinterconnected components commonly used in electrical switchgearsystems.

The switchgear frame 124 defines the upper and lower compartments 136,138 and a truck 144 is mounted for translatable and rotatable movementin each of the upper and lower compartments. Each truck 144 carries atleast one electrical component, such as a transformers 160 and fuses 162in the upper compartment 136 or a transformer 164 and fuses 162 in thelower compartment 138, and is supported for movement on the switchgearframe 124. In the example of FIG. 3 , the truck 144 in the uppercompartment 136 includes three fuses 162 and potential transformers(PTs) 160 corresponding to each phase of the three-phase circuit, whilethe lower compartment 138 includes a control power transformer 164 andfuses 162.

The drive mechanism 146 for each truck 144 in the upper and lowercompartments 136, 138 is supported on the switchgear frame 124 andconnected to each truck 144 and configured to rack that respective truckinto an electrically connected position with the at least one electricalswitchgear component 170, such as shown in FIG. 6A, in which electricalconnecting tabs 172 for the potential transformers 160 are connected toone or more switchgear electrical components, such as part of anelectrical bus, cable or other electrical components, and permitelectrical connection of the various transformers 160, 164 and otherelectrical components carried by the truck 144. Interconnection is madeto at least one electrical switchgear component 170, such as a circuitconnector, cable or bus, when the truck 144 is in that electricallyconnected position such as shown in FIG. 6A.

The drive mechanism 146 for each truck 144 located in each of the upperand lower compartments 136,138 is configured to rack out the respectivetruck in the respective compartment from the electrically connectedposition into an electrically disconnected position from the at leastone electrical switchgear component 170 as shown in FIGS. 2B and 6B,where both trucks 144 in upper and lower compartments extend slightlytoward the front (FIG. 6B).

The electrical connecting tabs 172 carried by the truck in the uppercompartment 136 and connected to the potential transformers 160 andfuses is disconnected from the electrical component 170, and thus, thepotential transformers 160 and fuses 162 in this example aredisconnected from the electrical component 170 as part of the electricalswitchgear circuit. A similar function exists with the control powertransformer 164 carried by the truck 144 in the lower compartment 138.

In order to allow a maintenance technician or other worker accesselectrical components carried by the truck 144, such as the fuses 162,control power transformers 164 or potential transformers 160, the drivemechanism 146 rotates the truck 144 upward from its disconnectedposition into its rotated position (FIGS. 3, 4C, 5, and 6C) to allowoperator access through the front opening 140 to the electricalcomponents carried on the truck, such as the fuses and/or transformers.

As shown in FIG. 3 , both trucks 144 are mounted in the upper and lowercompartments 136,138 and are rotated upward, and exposed for operatoraccess to the transformers 160,164 and fuses 162 mounted on the trucks(FIG. 6C). Examples of the connected, disconnected, and rotatedpositions are also shown in the isometric views of the truck 144 shownin FIGS. 4A, 4B and 4C.

The switchgear housing 104 as illustrated is formed in an example as ametal clad switchgear housing operable at medium voltage. Each truck144, as best shown in FIGS. 4A-4C, 5 and 6A-6C, includes a deck or floor176 and supporting front and rear rollers 178 a, 178 b at the fourcorners on the underside of the deck or floor 176 that permits the truckto roll on floor rails 180 (FIG. 5 ) positioned at the lower inside andside edge of each upper and lower compartment 136,138.

Each floor rail 180 in this example may be formed of a flat strip ofmetal on which the rollers 178 a, 178 b engage and roll (FIG. 5 ). Eachtruck 144 also includes a front wall 182 to prevent access to the fuses162 and transformers 160,164 when the trucks are racked into theelectrically connected position. Each truck 144 also includes sidewalls184 that are trapezoidal shaped with higher sides near the front wall182 to prevent the operator from reaching around and into the area ofthe truck holding the transformers 160, 164 and fuses 162 when the truck144 is in the electrically connected position with any electricalcomponents 170.

The drive mechanism 146 includes a leadscrew 186 (FIGS. 5 and 7 ) and alinkage 190 connected to the truck 144 and leadscrew (FIGS. 4C, 7 and 8). Rotation of the leadscrew 186 racks in and racks out the truck 144among the electrically connected position, the electrically disconnectedposition, and the rotated position shown in those three positionsillustrated at FIGS. 4A, 4B and 4C. In an example, the drive mechanism146 includes a leadscrew carrier housing 192 containing a nut having athreaded section that engages to and is carried by the leadscrew 186 andconnected to the linkage 190, which in an example is formed as a jackmechanism (FIGS. 5, 7, and 8 ), and more particularly, similar to ascissor jack as best shown in FIGS. 4C, 6C and 8 .

As shown in the sectional view of FIG. 6C, the leadscrew 186 may includea hex nut 194 at the front of the switchgear housing 104 that isconfigured to engage with an operator racking tool. An operator mayrotate the leadscrew 186 from the front by engaging a racking tool withthe hex nut and rotating the hex nut and leadscrew to rotate and rack inand rack out the truck 144 into the electrically connected, electricallydisconnected, and rotated positions. The switchgear frame 124 formingthe upper and lower compartments 136, 138 includes the floor rails 180and the truck 144 includes the front and rear rollers 178 a, 178 b thatsupport the truck for translational rolling movement along the floorrails 180 of the switchgear frame 124 between the electrically connectedposition and electrically disconnected position.

As best shown in FIGS. 4A-C, 5 and 6C, each floor rail 180 on the frame124 has an associated channel stop 196 towards the front section of theswitchgear frame 124, such as formed on the front frame section of thedrive mechanism 146. The channel stop 196 engages the front rollers 178a when the truck 150 is in the disconnected position to stop furthertranslational forward movement of the truck outward toward the frontopening 140 of the switchgear housing 104.

Upon further rotation of the leadscrew 186, the drive mechanism 146engages the linkage 190 as a jack mechanism pivots upward the bottomdeck 176 and raises the rear of the truck off its rear rollers 178 b androtates upward the truck 144 along a pivot defined by the axis of thefront rollers 178 a, such as a support rod or an axle 178 c connectingthe front rollers to each other and onto the underlying deck 176 of thetruck, such as via flanged side supports 176 a.

As shown in FIG. 8 , the linkage 190 as a jack mechanism includes a jackarm 198 as a rectangular configured support arm pivotally connected tothe leadscrew carrier housing 192, which in turn, is moved forward byrotation of the leadscrew 186. When the front rollers 178 a engage thechannel stops 196 at the front end of the floor rails 180, the jack arm198 is forced upward to rotate the truck 150 about a central axisdefined by the rod or axle 178 c and a pivot point. A bracket 200 mayinclude a support pin 202 connecting an end of the jack arm 198 onto thebracket positioned on the underside of the deck or floor 176 of thetruck 144.

This configuration of the truck 144 and drive mechanism 146 allows thecombination of translation and rotation of the truck 144, or draw-outdrawer as sometimes referred, to facilitate operator access to thetransformers 160,164 and fuses 162 for maintenance and service. Otherelectrical components may be carried on the truck 144, which may operateas an auxiliary draw-out tray for different switchgear electricalcomponents. In the various drawings, other components may be includedfor the truck 144 and drive mechanism 146 to facilitate operation andfunction. The plan and sectional views of the drive mechanism 146illustrate different views and show fasteners as bolts 204 (FIG. 8 ) toaid in retaining separate pieces together.

As illustrated in FIGS. 2A, 2B and 3 , the switchgear housing 104 isformed as a metal clad switchgear housing having overlaying metal sheetsto form top, bottom and sides, and help form the switchgear frame 124and includes at the sides the stepped offset 130. Each switchgearhousing 104, 106, 108, 110, 116, 118, 120, 122 shown in FIG. 1 mayinclude this formed stepped offset 130 to help in convective ventilationof air and gases, such as hot arc gases, which may occur during a shortcircuit.

The stepped offset 130 forms the ventilation duct 134 extending theheight of the front of the electrical switchgear system 100 (FIGS. 1 and26 ) to vent the interior compartments 128 of each switchgear housingvia the vents 131 a, 131 b formed in the side of the stepped offset 130.The doors 104 a, 106 a, 108 a, 110 a to each of the switchgear housings104 a, 106 a, 108 a, 110 a forming the front section 102 electricalswitchgear system 100 each may include differently configured vents. Inan example of the switchgear housing 104 of FIGS. 2A, 2B and 3 , aninterlock mechanism shown schematically at 210 interconnects the drivemechanism 146 in each of the upper and lower compartments 136, 138 tothe respective door 104 a and prevents the drive mechanism 146 fromrotating the truck into its rotated position unless the door is open.

This function prevents damage to components such as the transformers160,164 and fuses 162 when an operator rotates the leadscrew 186 beforethe truck 144 is rotated upward from its disconnected position into itsrotated position and prevents the truck and any electrical or othercomponents carried thereon from engaging directly with any electricalcomponents or circuits that may be mounted on the interior section ofthe door 104 a or hitting the inside of the door and damaging componentscarried by the truck 144.

As shown in FIG. 3 , the trucks 144 and the carried electricalcomponents, such as fuses 162 and transformers 160, 164, are partiallypositioned out of the front opening of each upper and lower compartment,and if the trucks are rotated while the door 104 a is closed, seriousdamage may occur to the transformers, fuses and other components carriedby the truck, and to any electrical components that are carried on theinterior of the door. The interlock 210 may be formed as anelectronically controlled latch or a spring loaded mechanism, such thatwhen the door 104 a is opened, the spring is released to allow the truckto be further translated and then rotated.

In another example, a maintenance technician may be forced to open thedoor 104 a and manually pull back on a safety slide (not shown), whichremoves a lock and allows rotation of the truck as a racking toolengaged to the hex nut 194 of the leadscrew 186 is rotated. The use ofmanual action from a maintenance technician may enhance safely since thetechnician must make a positive action of turning manually the rackingtool and leadscrew to move and then rotate the truck 144.

As noted before, the switchgear system 100 includes in this example alower, front switchgear housing 106 also having a switchgear frame 124and defining an interior compartment 128 and including in this example aprimary circuit 220 and a secondary control power or test circuit 222that operates as a test circuit (FIG. 9A). The primary circuit 220 mayconnect to primary bus components and output cables shown generally at224, and the secondary circuit 222 may connect to other control and testcircuits shown generally at 226. These electrical components may becontained in sections of the rear switchgear housings 116, 118, 120, 122and may operatively connect to a circuit breaker transformer and othercomponents.

As shown in FIGS. 9A and 9B, a circuit breaker truck 150 is configureddifferently than the trucks 144 of FIGS. 1-8 . This circuit breakertruck 150 is configured for linear movement in the interior compartment128 without being rotatable. For purposes of description, this truck 150will hereinafter be referred to as the C.B. truck 150 with C.B.corresponding to circuit breaker. This C.B. truck 150 is supported forlinear movement on the switchgear frame 124, in this example, movable onside rails 230 as shown in the interior view of a portion of theinterior compartment 128 at FIG. 14 , illustrating a side rail 230mounted on the interior inner side of the switchgear frame 124 and onwhich the front and rear rollers 232 a, 232 b are supported fortranslational rolling movement along the side rails 230 of theswitchgear frame 124.

A side rail 230 is mounted on each interior side of the switchgear frame124 and positioned a few inches above the bottom floor switchgearhousing 106 formed by the switchgear frame and metal cladding. In theexample shown in FIGS. 9A, 9B, and FIGS. 10-14 , the circuit breakerdrive mechanism 152 is mounted on the bottom floor of the switchgearframe 124 forming the switchgear housing 106 and connected to the C.B.truck 150, and configured to rack the C.B. truck and the circuit breaker250 it carries into a first connected position where the primarycircuits 220 and secondary control or test circuits 222 are electricallyconnected (FIGS. 9A and 9B), a test position where primary circuits areelectrically disconnected and the secondary circuits are connected and afully disconnected position where both primary and secondary circuitsare disconnected.

The circuit breaker drive mechanism 152 for purposes of description ishereinafter referred to as the C.B. drive mechanism 152 and is alsoconfigured to rack out the C.B. truck 150 and the circuit breaker 250into a second test position where the primary circuit 220 iselectrically disconnected and the secondary circuit 222 is connected tothe secondary control or test circuits, for example, such as fortesting.

An example of secondary connectors 252 as part of the secondary circuit222 are best shown in FIGS. 13 and 14 , allowing a cable or othersecondary connection to connect and complete the secondary circuit fortesting and/or control. The C.B. drive mechanism 152 is also configuredto rack out the C.B. truck 150 into a third disconnected position wherethe primary and secondary circuits 220, 222 are electricallydisconnected.

In this example as best shown in FIG. 11 , the C.B. drive mechanism 152includes a drive chain 254, and a shuttle 256 that connects twoseparated ends of the drive chain. The shuttle 256 is configured toengage the underside of the C.B. truck 150. As the drive chain 254rotates, the C.B. truck 150 will rack in and fix the circuit breaker 250into its first connected position where the primary circuit 220 and thesecondary circuit 222 are electrically connected.

First and second sprockets 260, 262 interconnect the drive chain 254(FIG. 11 ), corresponding to front and rear sprockets, with the first orfront sprocket 260 slightly smaller in diameter than the second or rearsprocket 262. Thus, the driving force or “holding” force exerted by thefirst, front smaller sprocket 260 onto the larger second rear sprocket262 enhances the holding or binding force that acts on the C.B. truck150. Large forces may be generated by a short circuit, for example.

A pin 266 is shown diagrammatically in FIGS. 11 and 13 , and may befixedly carried at the underside of the C.B. truck 150 and may lock theC.B. truck 150 to the shuttle 256 at a position adjacent the second orrear sprocket 262 when the circuit breaker 250 is in the firstelectrically connected position and electrically connected to primarycircuit 220 and secondary circuit 222. The shuttle 256 includes a slot268 that engages the pin 266 as the drive chain 254 and shuttle 256 arerotated forward, thus locking the shuttle 256 and C.B. truck 150together and maintaining a biasing force, such as when the circuitbreaker 250 is connected with the primary circuit 220 and an excessiveforce is generated such as a short circuit arc, which generates extremestresses on the C.B. truck 150 and C.B. drive mechanism 152.

The circuit breaker 250 as illustrated in FIGS. 9A and 9B is athree-phase circuit breaker and includes first, second and third vacuuminterrupters 270 that define three poles 272 for the three-phase circuitas first, second and third single-phase circuits with the upper portionof the poles each having a contact arm 274 that connects to a bus barcircuit, for example, as part of an input as a power supply and theprimary circuit and the lower portion of the poles each having a contactarm 276 having connectors to connect to a cable assembly or otherelectrical circuit as part of the output and connected to a load.

Although only one vacuum interrupter 270 and one pole 272 is illustratedin FIGS. 9A and 9B and associated pole, there are three vacuuminterrupters 270 and poles across the width of the truck 150. Eachvacuum interrupter 270 and pole 272 includes an upper contact arm 274and lower contact arm 276 and include connectors that include a contactfinger assembly shown generally at 280 and as best shown in FIG. 16 ,which are received into primary circuit bushings 282 that are formed asa primary circuit housing to hold fixed primary circuit contacts 220 aas shown in the dashed lines, and which engage the contact fingerassemblies 280 (FIGS. 9A and 9B).

The contact arms 274, 276 may carry a contact finger assembly 280 formedas tulip contacts in different configurations although a preferreddesign is illustrated in the example shown in FIG. 18 and explained ingreater detail below. Each vacuum interrupter 270 operates as a switchand incorporates a movable electrical contact and a fixed electricalcontact in a vacuum. The separation of the electrical contacts resultsin a metal vapor arc, which is quickly extinguished. This medium-voltageswitchgear system 100 includes the medium-voltage, three-phase vacuumcircuit breaker 250 having three vacuum-interrupters 270. Each vacuuminterrupter 270 provides the fixed and moving contact in a flexiblebellows to allow movement of the movable contact and in ahermetically-sealed ceramic with a high vacuum. Usually the bellows ismade of stainless steel.

Current commercially available vacuum interrupters have a very long MeanTime to Failure (MTTF), and include high technology ceramic housingsthat imparts a vacuum tightness with a resolution to the range of 10⁻⁷hPa. The three-phase vacuum circuit breaker 250 as illustrated mayoperate with protective relays and other sensors to detect overcurrentor other abnormal or unacceptable conditions and signal the circuitbreaker 250 and its vacuum interrupters 270 to switch open.

To maintain heat control, each pole 272 may include an insulator 284 asillustrated. The protective relays and sensors may be formed as currenttransformers and potential transformers and temperature or pressureinstruments and other sensing devices that may operate in the electricalswitchgear environment. The vacuum interrupters 270 may operate at 5 KV,15 KV, 27 KV, and 37 KV corresponding to the normal operating range ofmedium-voltage switchgear systems 100.

In this example best shown in FIG. 12 , the C.B. drive mechanism 152includes a worm drive mechanism 290 operatively connected to the firstor front sprocket 260 (FIG. 12 ). The worm drive mechanism 290 includesa worm shaft 292 configured at its end to have a nut 294 (FIG. 13 ) orother device to engage a racking tool that allows an operator to rotatethe worm shaft 292 the front sprocket 260 and the drive chain 254, andrack in and rack out the C.B. truck 150 and three-phase circuit breaker250 into the first electrically connected position, the second testposition, and the third disconnected position. Because the C.B. truck150 and circuit breaker 250 are both very large and heavy components, agear reducer 296 (FIG. 12 ) may be connected between the worm drivemechanism 290 and first sprocket 260 to provide gear reduction andtorsional force to move the C.B. truck when connected to the shuttle 256and reduce the amount of force and torque an operator must use to rotatethe worm shaft 292.

As shown in FIGS. 13 and 14 , the electrical contact connectors 252 maybe supported on the C.B. drive mechanism 152 to make contact with otherconnectors on the C.B. truck when racked forward, including secondarycircuit 222 connectors. The C.B. truck 150 includes front and rearrollers 232 a, 232 b that support the C.B. truck for translationalrolling movement along the side rails 230 positioned on the insideinterior sidewalls of the switchgear frame 124, and in this example, apair of side rails on which the rollers are supported.

Each side rail 230 includes a channel stop 298 positioned at the end ofeach side rail with one channel stop shown on the one side railillustrated in FIG. 14 and configured to “chock” or stop the rearrollers 232 b when the C.B. truck 150 is racked into the first connectedposition and the circuit breaker 250 connected to primary circuits 220.The gear reducer 296 and sprockets 260,262 impart a mechanical advantagefor the operator when inserting a heavy and large circuit breaker 250such as when racking the circuit breaker into its electrically connectedposition with the primary circuits 220.

The electrically connected position when the C.B. truck 150 and circuitbreaker 250 are racked in completely is advantageous for mechanicallyfixing the circuit breaker 250 into electrical contract with the primarycircuits 220 due to the proximity of the rear sprocket 262 to thelatched pin 266 and the secured connection of the C.B. drive mechanism152 to the switchgear frame 124. Very powerful electrical forces may begenerated, such as during a short circuit, and the C.B. drive mechanism152 engaging the C.B. truck 150 carrying the circuit breaker 250 isforced to stay within its connected position even when the powerfulshort circuit forces exert force against the C.B. truck.

A spring 300 (FIGS. 10, 12 and 13 ) may engage the switchgear frame 124and C.B. truck 150 or other electrical switchgear components and aid inbiasing the circuit breaker 250 and C.B. truck into connected and otherpositions. The shuttle 256 connects to end sections of the drive chain254 (FIG. 11 ) and the shuttle may be held in place by chain retainers302 on each end of the drive chain 254. Threaded tensioning bolts 304may connect the chain retainers 302 to the shuttle 256 and the bolts maybe turned to either increase chain tension, making the drive chain 254more taut, or decrease chain tension, making the drive chain less taut.

The drive chain 254 may be pulled tighter and more taut relative to theshuttle 256 by rotating the threaded tensioning bolts 304 in a firstdirection, or the tension released and backed off by rotating thethreaded tensioning bolts in the opposite direction. This configurationof the C.B. truck 150 is also advantageous because the C.B. truckcarrying the circuit breaker 250 is separate from the C.B. drivemechanism 152, instead of being incorporated as one integral unit as insome commercially available circuit breaker and switchgear designs. Thisstructure and configuration as described with reference to the exampleshown in FIGS. 9A, 9B and 10-14 also facilitates maintenance.

Referring now to FIGS. 15-17 , there is illustrated a shutter mechanism310 that operates as a protective shutter over the fixed primary circuitcontacts 220 a contained in the primary circuit bushings 282, e.g.,support housings, as part of the switchgear system 100. As noted before,the C.B. truck 150 carrying the circuit breaker 250 is supported forlinear movement on side rails 230 of the switchgear frame 124, and theC.B. drive mechanism 152 is mounted on the switchgear frame 124 andconnected to the C.B. truck 150 similar in configuration to theembodiment shown in FIGS. 9A-14 .

The shutter mechanism 310 is connected to the C.B. drive mechanism 152,and includes two parallel shutters 312,314 and formed as two parallelelongated sheets (FIG. 17 ) that are configured to cover the fixedprimary circuit contacts 220 a, and a shutter linkage 316 operativelyconnected to the C.B. drive mechanism 152 and shutters 312, 314. Theshutters 312, 314 are formed of an elongated strip that includes acentral section and opposing edge strip sections to form a concave likestructure to cover the primary circuit fixed contacts 220 a contained inthe bushings 282.

As the C.B. drive mechanism 152 racks in the C.B. truck 150 and circuitbreaker 250 into the electrically connected position, the shutterlinkage 316 moves the shutters 312,314 open (FIG. 15 ) to allow thecontact finger assembly 280 to engage the fixed primary circuit contacts220 a carried within the bushings 282. As the C.B. drive mechanism 152racks out the C.B. truck 150 and circuit breaker 250, the shutterlinkage 316 moves the shutters 312, 314 closed over the fixed primarycircuit contacts 220 a (FIG. 16 ). The fixed primary circuit contacts220 a include upper and lower fixed primary circuit contacts containedin the bushings 282 and covered by the respective upper and lowershutters 312, 314.

The upper primary circuit contacts 220 a, for example, may connect to aprimary bus component that connects to the incoming power line andmedium-voltage switchgear, and the lower fixed primary circuit contactsmay be coupled to an outgoing line, such as connected by cables andexiting the switchgear system 100 to various loads. The fixed primarycircuit contacts 220 a are contained in the upper and lower bushings 282that contain the fixed primary circuit contacts, and the respectiveupper and lower shutters 312, 314 are pivotally mounted on the bushings282 via opposing upper and lower shutter brackets 324, 326 that arepivotally mounted on the bushings 282 and pivotally moveable to pivotupper and lower shutters 312,314 over the respective upper and lowerfixed primary circuit contacts 220 a. In this example, because thecircuit breaker 250 is a three-phase circuit breaker, there are sixfixed upper and lower primary circuit contacts 220 a arranged in tworows having three phases each, corresponding to the three-phase primarycircuit and the three vacuum interrupters 270 and poles 272,corresponding to each single-phase of the three-phase circuit.

As illustrated in FIG. 17 , a cam support rod 330 is axially supportedby the second rear sprocket 262 and extends traversely out from eitherside of the second rear sprocket 262 and from the C.B. drive mechanism152. A cam 334 is mounted at either end of the cam support rod 330. Acam follower linkage arm 340 that includes a cam follower roller 342that engages the cams 334 is pivotally connected to each interiorsidewall in order to engage the cams.

The cam follower linkage arm 340 is positioned on each interior side andconnects to the shutter brackets 324, 326 via the shutter linkage 316and is configured to open and close the shutters 312, 314 based uponrotation of the cam 334. Each shutter linkage 316 includes first, lowerand second, upper vertical linkage arms 328 a, 328 b as shown in FIGS.15-17 with the lower end of the first arm 328 a connected to an end ofthe cam follower linkage arm 340 and the other end connected to thesecond, upper linkage arm 328 b. Each cam follower linkage arm 340 maybe pivotally mounted to a bracket 350 (FIG. 14 ) that holds an end ofthe cam support rod 330 on the interior side on the frame 124 andhousing wall, such as between the side rail 230, which is spaced fromthe interior sidewall of the switchgear frame 124 forming the switchgearhousing.

When each cam 334 is rotated up, each cam follower linkage arm 340 movesup and forces the first and second arms 328 a, 328 b of the shutterlinkage 316 up. The upper end of the first lower arm 328 a and lower endof the second upper arm 328 b are connected to side of the shutterbracket 326 to rotate the shutter 314 clockwise, while the shutter 312rotates counterclockwise from the upper arm movement 328 b connected toside of shutter bracket 324. Thus, the top shutter 312 rotatescounterclockwise over the fixed primary circuit contacts 220 a and thelower shutter 314 rotates clockwise over the fixed primary circuitcontacts (FIG. 16 ).

The configuration of the shutters 314, 316 as having a central mountingposition at a medial portion and the side segments that connect to thelower and upper arms 328 a, 328 b aids in this pivoting movement. Wheneach cam 334 is rotated down, each cam follower linkage arm 340 pivotsdown and pivots the shutters 312, 314 pivotally mounted on the bushings282 in a direction away from the primary circuit contact as the C.B.drive mechanism 152 racks the C.B. truck 150 and the circuit breaker 250into electrical connection with the fixed primary circuit contacts 220a.

In this example, each cam follower linkage arm 340 is pivotallyconnected at one end at one location such as on the frame and interiorsidewall, and the other end connected to the first lower arm 328 a ofthe shutter linkage 316. The upper end of the first lower linkage arm328 a is connected to the shutter bracket 326 and to the lower end ofthe second upper linkage arm 328 b, which connects onto the shutterbracket 324.

Both shutter brackets 324, 326 are pivotally connected to the respectivefixed contact bushings 282. The C.B. drive mechanism 152 includes thecomponents as described above, including the drive chain 254 connectedto the C.B. truck 150 and configured to rack in and rack out the C.B.truck 150 and circuit breaker 250, and the first and second sprockets260, 262 interconnecting the drive chain 254. The shuttle 256 is carriedby the drive chain 254 and the pin 266 locks the C.B. truck 150 to theshuttle 256 as an example described above.

The worm drive mechanism 290 is operatively connected to the firstsprocket 260 and includes the worm shaft 292 and nut 294 configured toengage an operator racking tool for rotating the worm shaft, thesprocket 260 and drive chain 254 and racking in and racking out the C.B.truck 150. The gear reducer 296 is connected between the worm drivemechanism 290 and first sprocket 260. The C.B. truck 150 includes thefront and rear rollers 232 a, 232 b. In this example, the C.B. truck 150has a width about the interior width of the switchgear frame 124 definedby the side rails 230 on which the front and rear rollers 232 a, 232 bof the C.B. truck 150 linearly moves. The shutter mechanism 310 isdifferent than many conventional shutters since it is not operated bythe circuit breaker.

Referring now to FIG. 18 , there is illustrated a contact arm assembly400 that may be used for the switchgear circuit breaker 250 such asillustrated in FIGS. 15 and 16 . This contact arm assembly 400 includesa contact arm 402 having a central axis and may be formed as a hollowtube to aid in cooling.

The contact arm 402 includes a first end 406 configured for electricalconnection with a pole of a circuit breaker, such as a vacuuminterrupter, and a second end 408 having a distal end 408 a defining ashoulder 410 and an engagement 412 that protrudes from the contact arm402 proximal to the shoulder 410. The second end 408 of the contact arm402 between the engagement 412 and shoulder 410 defines a tubularextension 416 of substantially one outer diameter and substantially oneinner diameter as shown in FIG. 18 .

A plurality of contact fingers 420 are mounted circumferentially on thesecond end 408 of the contact arm 402 and configured to electricallyengage a primary circuit contact 220 a. Each contact finger 420 mayinclude a body 422 having a depression that could be formed as groove orsocket as a receiver 426 that receives the engagement 412 for electricalcontact.

The body 422 of each contact finger 420 includes first and second ends430, 432 and an outer edge 434 configured to receive coil springs 440 ateach of the first and second ends. An inner edge 444 has the depressionas for example a groove or socket as the receiver 426 formed therein atthe second end 432. An annular ring 450 is received onto the shoulder410 of the contact arm 402 and includes an outer circumferential edgethat extends outward beyond the shoulder.

The medial portion of the inner edge 444 of the contact finger 420includes a slot 452 that receives the outer circumferential edge of theannular ring 450 and forms a pivot point allowing the first end 430 ofeach contact finger 420 to bias when a primary circuit contact 220 aelectrically engages the contact fingers 420. The inner edge 444 of eachcontact finger 420 includes a first inward curved section 456 extendingbetween the slot 452 and first end 430 and a second inward curvedsection 460 extending between the slot 452 and second end 432.

In an example, the engagement 412 may be formed as a plurality of ballsextending from the outer surface of the contact arm 402 and eachconfigured to be received within the depression as a groove or socket orother receiver 426 of a respective contact finger to which it engages.The depression as a groove or socket as a receiver 426 may be generallytrapezoidal shaped and each ball may be generally trapezoidal shaped asillustrated and configured for frictional engagement with thetrapezoidal shaped depression. In yet another example, the engagement412 may be formed as a circumferential ridge.

Each contact finger 420 may be formed as a medial straight edge segmenton the outer edge 434 extending between first and second ends 430,432.The contact arm 402 may be formed as a shaft having an outer taper 464extending from the engagement 412 away from the contact fingers 420. Thecontact arm 402 may be formed as a tube at the end proximal to thecircuit breaker pole to provide cooling and heat dissipation.

In operation, when the C.B. truck 150 carrying the circuit breaker isracked in, the fixed primary circuit contact 220 a may engage the firstends 430 of the plurality of contact fingers 420 that circumferentiallysurround the second end 408 of the contact arm 402. As illustrated, thatfirst end 430 of each contact finger 420 may be generally formed as aninward curved edge at that first end to permit the fixed primary circuitcontact 220 a to slide forward against each of the contact fingers andspread the contact fingers outward against the biasing force exerted bythe springs 440.

In this example, the annular ring 456 is received onto the shoulder 410of the contact arm 402, and the outer circumferential edge extendsbeyond the shoulder and engages the slot 452 at the medial portion ofthe inner edge of each contact finger and leaves some gap between theinner peripheral edge and the smaller outer surface at the distal enddefined by the second end 408 of the contact arm 402. This allows some“play” and aids the pivoting motion of the contact fingers 420 when thefirst ends 430 of the contact fingers engage the fixed primary circuitcontact 220 a. A separate lock ring 466 may be positioned on the distalend 408 a of the contact arm 402 at the shoulder 410 and aid inretaining the annular ring 450 onto the distal end and the shoulder.

Referring now to FIGS. 1 and 19-26 , there is best illustrated how theelectrical switchgear system 100 includes an improved convectiveventilation system. As shown in FIG. 1 , the front switchgear section102 includes first and second sets of front and upper and lowerswitchgear housings 104, 106, 108, 110 having sidewalls and joinedtogether, and a rear switchgear section 114, including first and secondsets of rear upper and lower switchgear housings 116, 118, 120, 122having sidewalls and joined together and connected to the rear walls ofthe respective front upper and lower switchgear housings.

The sidewalls of first and second sets of front and rear upper and lowerswitchgear housings include the stepped offset section 130 as best shownin the switchgear housing examples of FIGS. 2A, 2B and 3 . When joinedtogether, the stepped offset sections 130 form a ventilation duct 134extending the height of the external switchgear system 100 defined bythe various switchgear housings.

Referring to the schematic, isometric views of FIGS. 19 and 20 , upperand lower vents 131 a, 131 b are formed in the stepped offset sections130 of the first and second sets of switchgear housings 102, 114 to ventthe interior compartment 128 of the switchgear housings into theventilation duct 134 as shown by the air and gas flow diagram in FIG. 20, where the air and gas flow is illustrated by the arrows, which aids inventilation when excess heat is generated by switchgear components, andalso aid in ventilation of the hot gases when arcing occurs such as witha short circuit.

In an example, the upper and lower vents 131 a, 131 b, which arecontained within the ventilation duct 134, are formed in each steppedoffset section 130. “N” sets of both front and rear upper and lowerswitchgear housings 102, 114 may be incorporated together, resulting ina wide switchgear system 100 having three, four or more switchgearhousings placed adjacent in side-by-side relation to each other. Becauseeach switchgear housing includes the stepped offset section 130 andupper and lower vents 131 a, 131 b, the outer sidewalls of theswitchgear system 100 will have exposed stepped offset sections as bestshown in FIGS. 19, 20 and 21 , and thus, include vents 131 a, 131 bexposed to the outside of the switchgear system.

The top plan view of FIG. 23 shows how the ventilation duct 134 ispositioned and allows air and gas to vent as shown in the enlargedsectional views of FIG. 25 taken from FIG. 24 , showing the verticalchannel formed by the ventilation duct. A vent cover 132 may bepositioned over the vents 131 a, 131 b in the ventilation duct 134 anddirect the hot air from inside the switchgear housings to pass byconvection out the ventilation duct 134 as shown in the schematic,sectional view of FIG. 26 taken along line 26-26 of FIG. 1 to illustratethe ventilation duct and the vent covers. The vent covers 132 may beformed as L-shaped brackets as shown in the central portion of thesectional view of FIG. 26 and help direct the hot air.

In an example, the switchgear housings 104-122 may include differentelectrical components as explained above and may include the truck 144or C.B. truck 150 carrying components such as a circuit breaker ortransformers. The front and rear switchgear sections 102, 114 mayinclude “n” sets of both front and rear upper and lower switchgearhousings having joined sidewalls, and stepped offset sections 130 toform a plurality of ventilation ducts 134. At least one of front andrear switchgear sections 102, 114 shown in FIG. 1 may include bus, cableand other compartments.

Referring now to FIG. 27 , there is illustrated a schematic diagram of amedium-voltage switchgear system 500 incorporated within a three-phasepower distribution grid 502 that includes a three-phase input 504 havingfirst, second and third single-phase input circuits 504 a, 504 b, 504 c.The switchgear system 500 includes single phase breaker control thatallows the switchgear system to provide single phase control at thethree-phase switchgear circuit breaker 510 such that a single phase linemay power a neighborhood or a part of a residential tower when asingle-phase line may go down.

Other neighborhoods or street sections as schematically illustrated bythe block indicated as loads 514 for the loads, and may include floorareas of the skyscraper supplied by the other two single-phases and mayhave power. For example, the top apartments in a residential tower mayhave a short circuit in that single-phase segment and that single-phasemay be tripped at the single-phase pole, e.g., a vacuum interrupter forthat phase, but the bottom sections of the residential tower may havepower provided from the other two single phase circuits and stillmaintain power.

The switchgear system 500 may include the components as described beforesuch as the switchgear frame having an interior compartment and first,second and third single-phase inputs 504 a, 504 b, 504 c and first,second and third single-phase outputs 524 a, 524 b, 524 c connected tothe respective first, second and third single-phase circuits of thethree-phase power distribution grid 502. Primary and secondary circuitsas described before may be included and a C.B. truck 150 and thethree-phase circuit breaker 510 may be carried thereon and supported forlinear movement on side rails provided on the switchgear frame such asdescribed above.

As illustrated in FIG. 27 , the three-phase circuit breaker 250 includesfirst, second and third single-phase vacuum interrupters 526 a, 526 b,526 c configured to be connected between the respective first, secondand third single-phase inputs 504 a, 504 b, 504 c and first, second andthird single-phase outputs 524 a, 524 b, 524 c. A first magneticactuator M1 is connected to the first single-phase vacuum interrupter526 a. A second magnetic actuator M2 is connected to the secondsingle-phase vacuum interrupter 526 b. A third magnetic actuator M3 isconnected to a third single-phase vacuum interrupter 526 c. Eachmagnetic actuator M1, M2, M3 is configured to receive an interruptsignal and in response, actuate the respective vacuum interrupter 526 a,526 b, 526 c connected thereto into an open circuit condition.

A controller circuit 534 is connected to each of the first, second andthird magnetic actuators M1, M2, M3 and configured to generate theinterrupt signal to a respective magnetic actuator in response to adetected single-phase overcurrent or fault on a single-phase circuit aspart of the load 514 and interrupt that single-phase circuit on whichthe single-phase overcurrent or fault occurred and maintain power on theremaining two single-phase circuits over which a single-phaseovercurrent or fault is not detected.

The controller circuit 534 may be formed as a first controller 534 amounted within the interior compartment and connected to the firstmagnetic actuator M1. A second controller 534 b may be mounted withinthe interior compartment and connected to the second magnetic actuatorM2. A third controller 534 c may be mounted within the interiorcompartment and connected to the third magnetic actuator M3. In anotherexample, the controller circuit 534 may be formed as a single controllermodule mounted within the interior compartment and connected to each ofthe first, second and third magnetic actuators M1, M2, M3.

The loads 514 may include first, second and third single-phase loads andare connected to respective first, single and third single-phase outputs524 a, 524 b, 524 c, such as the plurality of floors in an apartmentbuilding having an electrical demand operating with single-phase, e.g.,the top floors are powered by a single-phase line, the mid-floors arepowered by the second single-phase line, and the bottom floors arepowered by the third single-phase line. In another example, the first,second and third loads may be a business that uses three-phase power anda group of homes that use a single-phase power.

A sensing circuit 540 may be connected to the first, second and thirdsingle-phase outputs 524 a, 524 b, 524 c and configured to detect asingle-phase overcurrent or fault in the first, second and thirdsingle-phase circuits. The controller circuit 534 may receive data fromthe sensing circuit 540 and may generate an interrupt signal to arespective magnetic actuator M1, M2, M3 to actuate and move the movablecontact of the vacuum interrupter away from its fixed contact and openthe circuit. The sensing circuit 540 may be formed as a current orpotential transformer or other similar sensing devices.

As described before, the switchgear system 500 may include a switchgearhousing and frame 124 having a C.B. drive mechanism 152 mounted on theswitchgear frame and connected to the C.B. truck 150 and configured torack the truck and circuit breaker carried thereon into a firstconnected position where the primary and secondary circuits areelectrically connected, rack out the truck into a second test positionwhere a primary circuit is electrically disconnected and a secondarycircuit connected, and rack out into a third disconnected position wherethe primary and secondary circuits are electrically disconnected. Thecontroller circuit 534 may be formed as a microcontroller or otherprocessor and may be part of the circuit breaker and connected to eachof the first, second and third magnetic actuators M1, M2, M3.

Many modifications and other embodiments of the invention will come tothe mind of one skilled in the art having the benefit of the teachingspresented in the foregoing descriptions and the associated drawings.Therefore, it is understood that the invention is not to be limited tothe specific embodiments disclosed, and that modifications andembodiments are intended to be included within the scope of the appendedclaims.

1. A medium-voltage switchgear system, comprising: a switchgear framehaving a plurality of interior compartments, each of the interiorcompartments having: first, second and third single-phase inputs, first,second and third single-phase outputs connected to a respective one offirst, second and third single-phase circuits of a three-phase powerdistribution grid, a three-phase circuit breaker comprising: first,second and third single-phase vacuum interrupters configured to beconnected between respective pairs of the first, second and thirdsingle-phase inputs and the first, second and third single-phaseoutputs, a first magnetic actuator connected to the first single-phasevacuum interrupter, a second magnetic actuator connected to the secondsingle-phase vacuum interrupter, and a third magnetic actuator connectedto the third single-phase vacuum interrupter, wherein each of the first,second and third magnetic actuators configured to receive an interruptsignal and in response, actuate a respective one of the first, secondand third single-phase vacuum interrupters connected thereto into anopen circuit condition; and a controller circuit mounted within arespective one of the interior compartments and separate from thethree-phase circuit breaker, the controller circuit connected to each ofsaid first, second and third magnetic actuators, the controller circuitconfigured to generate the interrupt signal to at least one of thefirst, second and third magnetic actuators in response to a detection ofa single-phase overcurrent or fault on at least one of the first, secondand third single-phase circuits and interrupt the respective at leastone of the single-phase circuits on which the single-phase overcurrentor fault occurred and maintain power on any remaining first, second andthird single-phase circuits over which a single-phase overcurrent orfault was not detected.
 2. The medium-voltage switchgear system of claim1 wherein said controller circuit comprises: a first controller mountedwithin the respective one of the interior compartments and connected tothe first magnetic actuator, a second controller mounted within therespective one of the interior compartments and connected to said secondmagnetic actuator, and a third controller mounted within the respectiveone of the interior compartments and connected to said third magneticactuator.
 3. The medium-voltage switchgear system of claim 1 whereinsaid controller circuit comprises a controller mounted within therespective one of the interior compartments and connected to each ofsaid first, second and third magnetic actuators.
 4. The medium-voltageswitchgear system of claim 1 further comprising first, second and thirdloads connected to a respective one of the first, second and thirdsingle-phase outputs.
 5. The medium-voltage switchgear system of claim 4wherein said first, second and third loads each comprise a plurality offloors in an apartment building having an electrical demand operatingwith single-phase power.
 6. The medium-voltage switchgear system ofclaim 4 wherein said first, second and third loads comprise a businessusing three-phase power and a group of homes using single-phase power.7. The medium-voltage switchgear system of claim 1 further comprising asensing circuit connected to said first, second and third single-phaseoutputs, the sensing circuit configured to detect the first, second andthird single-phase overcurrents or faults on the respective single-phasecircuit of said first, second and third single-phase circuits.
 8. Themedium-voltage switchgear system of claim 7 wherein said sensing circuitcomprises at least one current or potential transformer.
 9. Amedium-voltage switchgear system, comprising: a switchgear frame havinga plurality of interior compartments, each of the interior compartmentshaving: first, second and third single-phase inputs, first, second andthird single-phase outputs connected to a respective one of first,second and third single-phase circuits of a three-phase powerdistribution grid, a truck and a three-phase circuit breaker carried onthe truck, the truck supporting the three-phase circuit breaker formovement within a respective one of the interior compartments, saidthree-phase circuit breaker comprising: first, second and thirdsingle-phase vacuum interrupters configured to be connected betweenrespective pairs of the first, second and third single-phase inputs andthe first, second and third single-phase outputs, a first magneticactuator connected to the first single-phase vacuum interrupter, asecond magnetic actuator connected to the second single-phase vacuuminterrupter, and a third magnetic actuator connected to the thirdsingle-phase vacuum interrupter; wherein each of the first, second andthird magnetic actuators configured to receive an interrupt signal andin response, actuate a respective one of the first, second and thirdsingle-phase vacuum interrupters connected thereto into an open circuitcondition; a drive mechanism mounted on respective one of the interiorcompartments, the drive mechanism connected to the truck and configuredto rack the truck and first, second and third single-phase vacuuminterrupters into electrical connection with the respective pairs of thefirst, second and third single-phase inputs and the first, second andthird single-phase outputs; and a controller circuit mounted within therespective one of the interior compartments and separate from thethree-phase circuit breaker, the controller circuit connected to each ofsaid first, second and third magnetic actuators, the controller circuitconfigured to generate the interrupt signal to at least one of thefirst, second and third magnetic actuators in response to a detection ofa single-phase overcurrent or fault on at least one of the first, secondand third single-phase circuits and interrupt the respective at leastone of the single-phase circuits on which the single-phase overcurrentor fault occurred and maintain power on any remaining first, second andthird single-phase circuits over which a single-phase overcurrent orfault was not detected.
 10. The medium-voltage switchgear frame of claim9 further wherein said first, second and third single-phase inputs andsaid first, second and third single-phase outputs comprise a primarycircuit and a secondary circuit, and said drive mechanism is configuredto rack the truck and the three-phase circuit breaker into a) a firstconnected position where the primary and secondary circuits areelectrically connected, b) a second test position where the primarycircuit is electrically disconnected and the secondary circuit iselectrically connected, and c) a third disconnected position where theprimary and secondary circuits are electrically disconnected.
 11. Themedium-voltage switchgear system of claim 9 wherein said controllercircuit comprises: a first controller mounted within the respective oneof the interior compartments and connected to the first magneticactuator, a second controller mounted within the respective one of theinterior compartments and connected to said second magnetic actuator,and a third controller mounted within the respective one of the interiorcompartments and connected to said third magnetic actuator.
 12. Themedium-voltage switchgear system of claim 9 wherein said controllercircuit comprises a controller mounted within the respective one of saidinterior compartments and connected to each of said first, second andthird magnetic actuators.
 13. The medium-voltage switchgear system ofclaim 9 further comprising first, second and third loads connected to arespective one of the first, second and third single-phase outputs. 14.The medium-voltage switchgear system of claim 13 wherein said first,second and third loads comprise a plurality of floors in an apartmentbuilding having an electrical demand operating with single-phase power.15. The medium-voltage switchgear system of claim 13 wherein said first,second and third loads comprise a business using three-phase power and agroup of homes using single-phase power.
 16. The medium-voltageswitchgear system of claim 9 further comprising a sensing circuitconnected to said first, second and third single-phase outputs, thesensing circuit configured to detect the first, second and thirdsingle-phase overcurrents or faults on the respective single-phasecircuit of said first, second and third single-phase circuits.
 17. Themedium-voltage switchgear system of claim 16 wherein said sensingcircuit comprises at least one current or potential transformer.
 18. Amethod of operating a medium-voltage switchgear system, comprising:connecting respective pairs of first, second and third single-phaseinputs and first, second and third single-phase outputs contained withina respective one of a plurality of interior compartments of a switchgearframe to a respective one of first, second and third single phasecircuits of a three-phase power distribution grid; providing athree-phase circuit breaker within the respective one of the interiorcompartments, the three-phase circuit breaker comprising: first, secondand third single-phase vacuum interrupters between the respective pairsfirst, second and third single-phase inputs and the first, second andthird single-phase outputs, a first magnetic actuator connected to thefirst single-phase vacuum interrupter, a second magnetic actuatorconnected to the second single-phase vacuum interrupter, and a thirdmagnetic actuator connected to the third single-phase vacuuminterrupter, wherein each of the first, second and third magneticactuators configured to receive an interrupt signal and in response,actuate a respective one of the first, second and third single-phasevacuum interrupters connected thereto into an open circuit condition;receiving the interrupt signal within one of the first magneticactuator, the second magnetic actuator, and the third magnetic actuator,and in response, actuating the respective one of the first, second andthird single-phase vacuum interrupters connected thereto into the opencircuit condition; and generating the interrupt signal via a controllercircuit mounted within a respective one of the interior compartments andseparate from the three-phase circuit breaker, the controller circuitconnected to each of said first, second and third magnetic actuators,the controller circuit configured to generate the interrupt signal to atleast one of the first, second and third magnetic actuators in responseto a detection of a single-phase overcurrent or fault on at least one ofthe single-phase circuits of the first, second and third single-phasecircuits and interrupt the respective at least one of the single-phasecircuits on which the single-phase overcurrent or fault occurred andmaintain power on any remaining first, second and third single-phasecircuits over which a single-phase overcurrent or fault was notdetected.
 19. The method of claim 18 wherein said controller circuitcomprises: a first controller mounted within the respective one of theinterior compartments and connected to the first magnetic actuator, asecond controller mounted within the respective one of the interiorcompartments and connected to said second magnetic actuator, and a thirdcontroller mounted within the respective one of the interiorcompartments and connected to said third magnetic actuator.
 20. Themethod of claim 18 wherein said controller circuit comprises acontroller mounted within the respective one of the interior compartmentand connected to each of said first, second and third magneticactuators.
 21. The method of claim 18 further comprising connectingfirst, second and third loads to a respective one of the first, secondand third single-phase outputs.
 22. The method of claim 21 wherein saidfirst, second and third loads each comprise a plurality of floors in anapartment building having an electrical demand operating withsingle-phase power.
 23. The method of claim 21 wherein said first,second and third loads comprise a business using three-phase power and agroup of homes using single-phase power.
 24. The method of claim 18further comprising connecting a sensing circuit to said first, secondand third single-phase outputs, the sensing circuit configured to detectthe first, second and third single-phase overcurrents or faults on therespective single-phase circuit of said first, second and thirdsingle-phase circuits.
 25. The method of claim 24 wherein said sensingcircuit comprises at least one current or potential transformer.